EnumerableCount Method

Returns a number that represents how many elements in the specified sequence satisfy a condition.

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

public static int Count<TSource>(
	this IEnumerable<TSource> source,
	Func<TSource, bool> predicate
generic<typename TSource>
static int Count(
	IEnumerable<TSource>^ source,
	Func<TSource, bool>^ predicate
static member Count<'TSource> : 
        source:IEnumerable<'TSource> *
        predicate:Func<'TSource, bool> -> int
Public Shared Function Count(Of TSource) (
	source As IEnumerable(Of TSource),
	predicate As Func(Of TSource, Boolean)
) As Integer



A sequence that contains elements to be tested and counted.


A function to test each element for a condition.

Return Value


A number that represents how many elements in the sequence satisfy the condition in the predicate function.

Type Parameters


The type of the elements of source.

Exception Condition

source or predicate is null.


The number of elements in source is larger than MaxValue.

If the type of source implements ICollection, that implementation is used to obtain the count of elements. Otherwise, this method determines the count.

You should use the LongCount method when you expect and want to allow the result to be greater than MaxValue.

In Visual Basic query expression syntax, an Aggregate Into Count() clause translates to an invocation of Count.

The following code example demonstrates how to use Count to count the elements in an array that satisfy a condition.

class Pet
    public string Name { get; set; }
    public bool Vaccinated { get; set; }

public static void CountEx2()
    Pet[] pets = { new Pet { Name="Barley", Vaccinated=true },
                   new Pet { Name="Boots", Vaccinated=false },
                   new Pet { Name="Whiskers", Vaccinated=false } };

        int numberUnvaccinated = pets.Count(p => p.Vaccinated == false);
        Console.WriteLine("There are {0} unvaccinated animals.", numberUnvaccinated);
    catch (OverflowException)
        Console.WriteLine("The count is too large to store as an Int32.");
        Console.WriteLine("Try using the LongCount() method instead.");

// This code produces the following output:
// There are 2 unvaccinated animals.
Structure Pet
    Public Name As String
    Public Vaccinated As Boolean
End Structure

Public Shared Sub CountEx2()
    ' Create an array of Pet objects.
    Dim pets() As Pet = {New Pet With {.Name = "Barley", .Vaccinated = True},
                 New Pet With {.Name = "Boots", .Vaccinated = False},
                 New Pet With {.Name = "Whiskers", .Vaccinated = False}}

        ' Count the number of Pets in the array where the Vaccinated property is False.
        Dim numberUnvaccinated As Integer =
    pets.Count(Function(p) p.Vaccinated = False)
        ' Display the output.
        MsgBox("There are " & numberUnvaccinated & " unvaccinated animals.")
    Catch e As OverflowException
        MsgBox("The count is too large to store as an Int32. Try using LongCount() instead.")
    End Try

End Sub

' This code produces the following output:
' There are 2 unvaccinated animals.
Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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